Radio distributing system



July 5,1927. 1,635,151

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k a O O O O OOOO Patented July 5, 1927.

UNITED STATES 1,635,151 PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO EDWARD F. COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

RADIO nrsrnrsurnve SYSTEM.

Application filed December 21, 1923, Serial No. 681,991. Renewed March 8, 1927.

My invention relates to systems of communication, and particularly to broadcasting systems.

The present application is a continuation in part of my copending application, Serial Number 581,829, filed Aug. 14, 1922, Patent Number 1,522,357, reissued as Reissue No. 16,231, and has for its objects, among others, the following: To organize broadcasting service on a commercial basis, and to control .the service units or receiving stations so that the various contingencies incidental to commercial operation may be efficiently met, such as maintenance, supervision, and the imposition and collection of charges; to localize each unit of a system, so that it may be tested and supervised; to standarize the distributed unit agencies in a system, while enabling them to receive messages broadcasted on various wave lengths; to control broadcasting so that it may supplement in organized service existing telephone eX- change systems.

The foregoing objects are attained by the method of opera-tlon to be hereinafter described, which, it 1s to be understood, is

typical, and is to be takenas such, for purposes of definition and not of limitation of the invention. According to this method I provide asystem having for its basis the distribution among regular subscribers in localized areas, of standardized receiving instruments, each local area taking its broadcasting service,,by wire guided waves, from its own central station on such wave length or frequency as may be fixed and determined for that area. Each receiving station is connected to the local central station by a wire circuit, through which both distribution and the controlof the local station are attained. This arrangement enables me conveniently to feed the substations with current from central for divers purposes, to control the receiving instruments at said stations from the central station, and to meter the broadcast service rendered for the purpose of making charges. Other benefits flowing from this arrangement will sufficiently appear from the detailed description hereinafter.

By using standardized receiving units, all uniformly tuned with their line circuits to the wave length of the local distributing station, I am able to provide said distributing station with sensitive and powerful receiving and relaying apparatus and circuits, whereby distant stations may be picked up, and various wave lengths may be received by variable tuning and their modulations relayed .over the wires on the standard local wave length to the subscribers, who can receive and recognize the original messages thus relayed, without the necessity of variable tuning or highly sensitive instruments at their stations. With the above arrangement for distribution, the ultimate receiving instruments are reduced to the simplest form compatible with their purpose because they are practically unaffected by atmospheric conditions or static, and when once tuned remain in tune, unless it is desired to give a small range of adjustment for sharpening.

My invention is "illustrated in the accompanying drawings in which Fig. 1 is a diagram showing a general system embodying the same;

Fig. 2 is a diagram showing a central station telephone switchboard, subscribers lines terminating thereon, and subscribers telephones connected thereto;

Fig. 3 is adiagram to be read in connection with Fig. 2, showing the broadcast receiving set at one of the subscribers stations, and the radio switchboard and associated equipment at the central station;

Fig. 4 is a diagram showing a substation battery charged and controlled over a phantom circuit imposed on a metallic magneto telephone circuit;

Figs. 5, 6, 7 and 8 are schematic circuits showing methods of connecting the radio battery with relation to the centralized telephone battery; and

Fig. 9 is a diagram ofa modified arrangement of circuits.

Fig. 10 is a circuit diagram of a modification of the system, for broadcasting over the wires;

Fig. 11 is a-diagram of a broadcast relay unit adapted for'use with the circuits of Fig. 10. V

Figs. 12, 13,- 14, and are simplified or schematic diagrams of different conditions of the circuits. under different conditions of service.

Referring to Fig. l, 1, 2 and 3 represent telephone subscribers stations connected by wires 4:, 5 and 6 to the central telephone exchange 7, constituting the distributing cen ter for the ar'ea in which local subscribers 1, 2, 3, etc., are located. Superposed upon this telephone system is a radio telephone system comprising a central station 8 and subscribers stations 1, 2, 3 etc. The cen tral radio station or exchange is provided with switchboards and a complete broadcasting equipment, and the subscribers stations 1", 2, 3 etc, are provided with receivlng instruments all standardized for the same wave length, and adapted to respond to the waves radiated from the central station 8. The interrelation between the telephone system and the radio telephone system is by means of physical connections indicated at 1 2 and 3' at the subscribers stations, and multiples or trunk extensions 15 from the telephone exchange switchboards to the radio broadcast service switchboard in station No. 8. The detail of these connections will appear hereinafter, but it should be stated here that the system oi connections is such that telephone wired tratlic has the right of ,way over the wires, while the radio traffic has the right of way over the radio side of the system. The arrangement is such that the radio operator cannot interfere with telephone operation, nor can a telephone operator interfere with the radio operation, although under proper conditions each can act freely by way of borrowing facilities from the other. At all times, should a question of precedence arise, the apparatus is arranged so as automatically to out off the radio connections and to leave the wired lines clear for telephonic use.

Stations 12, 13 and 1 1 in this figure are typical of indiflerently located distant stations which may or may not be a part of this particular system. As the figure is typical only, no attempt has been made to give the geographical location of such stations or to show the actual arrangement and distribution of the telephone centers through which final broadcasting to the subscribers must take place, The main purpose of this figure is to crystallize the method employed, by which the development of a very large number of unrelated individual receiving stations is replaced by an orderly system of distribution through the telephone centers, whereby the individual receiving instruments are localized, maintained, controlled, and supplied with definite service through regular channels, for which a definite charge can be made and collected in the manner usual in wired systems of communication. Inasmuch as the number of wave lengths available for transmission is limited in the present state of the art, advantage is taken of the organized system of wir'e distribution and localization to create a phantom system controlled and guided thereby.

Briefly stated, as indicated in Fig. 1, each radio central station or radio department of a telephone exchange, is not only provided with broadcasting equipment for its subscribers, but also with radio receivers adjustable by tuning to wave lengths allotted to such stations as those indicated at 12, 13 and 1 1, as well as primary stations maintained and operated by or under the direction of the telephone organization itself. By means understood in the art, messages received at the radio central stations are relayed on their respective standard Wave lengths to the local subscribers.

Referring to Figs. 2 and 3, I have therein shown circuits of the central ollice and substation equipments and connections, Fig. '2 representing the telephone side of the system, and Fig. 3 the radio broadcast side of the system. Before proceeding to detail de scription itmay be noted that in accordance with standard telephone practice, provision is made for keeping the. telephone lines and central otlice circuits clear of all grounds or other disturbing connections during conversation. When the broadcast receiving goes into service, by closing the filament switch its operation in receiving is identical with that of any radio receiver, and in the event that use is made of any transmission of waves over the line wires, as .Will be hereinafter pointed out, said waves will be at a frequency above or below the limits of audition. In the present diagram, Figs. 2 to 9 inclusive, 1 haveshown the circuits arranged with nothing but continuous current for radio purposes over the telephone line wires. This is the simplest form of control and the one nearest to presentday telephone practice, and is absolutely certain not to produce any disturbance in adjacent conductors in the telephone cables. Each broadcast receiving set is provided with a cut off relay energized when the telephone set goes into commission, either by calling or being called, and at the central ollice whenever the radio operator takes control of the line, he disables it in the usual manner by pulling up the cut oil relay at the telephone switchboard, this however being subject to the condition that a special tone test may be put on, so that all operators may know that the line is held on the radio board, and subject to interruption for telephone connection, I prefer to use this tone test only with the radio operator-"s testing plug, because his regular connecting plug includes within its functions that of connecting a subscriber through the station amplifier to the broadcasting transmitting set, and a connection of this character should not be interrupted without permission.

Referring now to the diagrams, Fig. 2, A and A are two subscribers stations connected by line wires 16-17 and 1819 respectively to the central station O wherethey terminate on jacks J and J. PP are peating COll I, ringing and listening keys K and K, supervisory signals s-s and bridging connection to the main battery B. The same battery is shown supplying current to the'line relays L, L, and through contacts at the cut off relays L L to the respective lines for calling purposes. In this system, when a subscriber takes down his receiver, the line relay lights its lamp, which is extinguished when the operator inserts the answering plug. Battery supply for the connected lines is thereafter taken through the cord circuit 20-22, 21-23, in a manner well understood in the art. When the substation telephones are out of service, with their receivers hanging on their hooks, the line circuits are conductively open for direct current, leaving the ringers Q and Q in circuit for alternating ringing current passing through the condensers gg.

Referring now to Fig. 3, it will be ob served that the radio switchboard which I have designated generally by the letter R, is connected to the subscribers lines by multiple taps marked 16*, 17 and 17 and 18 19 19- These terminate on multiple jacks J J corresponding to the multiple jacks on the telephone switchboard. These multiple connections 16*, 17", etc., instead of being permanently connected to the subscribers multiple jacks, trunks, less in number than the number of lines and terminating in plugs or jacks near the telephone,switchboards. This would be desirable where changes of terminal connections in the standard wiring are to be avoided, and would be especially advantageous where the proportion of subscribers taking special service is small. It should be noted that throughout this system the tip wires 16 and 18 with their branches are connected to ground, while the ring wires 17 and 19 and their branches, are connected to battery. This is extended into the radio side of the system for the purpose of securing proper balance between the main bat tery or power plant of that side and the main battery or power plant of the telephone side of the system.

At the subscribers stations taps are also taken off from the telephone terminals to the broadcast receiver terminals as indicated at 18, 19, and 19. (The broadcast receiver is shown only at .one substation for sake of simplicity of illustration. The two branches 19 and 19 are taken from the ring or battery side of the line 19, and are connected to opposite terminals of the winding of a relay L which constitutes the substation cut off relay for the radiophone. The winding of this relay is bridged by a condenser 9 through which both ringing and voice currents can pass may take the form of order a without substantial impedance. WVhere the radiophone is attached to a party line substation, this "relay L may be omitted, since on such party lines there are usually grounds on one side or the other. As will presently appear, the "adio circuits described herein are applicable to' two-party or four-party lines, with individual meteringof the party stations.

Normally, that 1s to say, when the telephone CllClll't'lS not in use, the cut oil relay L is deenergized and as'a consequence the wire 19 is connected through a back contact of the relay through extension wire 2 k to the branch 25 connected to the A battery marked A in'Fi g. 3. The wire 18 similarly passes through a back contact of the relay to the extension wire 26 leading to test or listening relay L and ground. 18, it will be remembered, leads to the tip or ground side of the line, therefore it is the side which in the broadcastreceiver can be made use. of with a permanent ground or grounds, without'disturbing-the balance of the telephone circuit.

The broadcast receiver .at the substation A is shown as comprising an antenna 28, tuned coupler29, detector tube 30, audio amplifier tubes 31 and 32, and the usual transformers 33, 34, 35, the last mentioned transmitting the amplified audio waves to the telephone receiver or loud speaker 36. The filament battery is A The plate battery is B, and suitable tuning condensers and coils, tickler coil for regenerative effects,

etc., are provided as required. I should reof the radio receiver is intended to be typi-' cal only. The present invention does not concern itself specifically with the design of the local broadcast receiver sets, and other circuits and apparatus may be substituted for those shown in the diagrc ms without departure from the invention.

The relay L has four pairs of contacts, one pair 27% closing the wires 25 and 37- from battery A to the filaments. The second pair 27 closes the wires 25 and 38 so as to put battery A, on the broadcast transmitter T, and through the induction coil I, to ground. The third and fourth pairs of contacts 27, 27, close the wires 39 and 40, forming terminals of the secondary induction coil circuit 1, to the tip and sleeve side oft-he telephone line respectively, through the back contacts of relay L. The transmitter T is shown hanging upon a hook switch H controlling the connection of wires 41 and 42, constituting a parallel link. between the battery A and the filament bus 13. Thus the filament can be heated and the the latter by the subscriber at the substation. In addition to the hook, the subscriber has a manual switch it by which he can con nectthe battery wire at?! through a wire si l to his transmitter T, coil and ground, so as to energize his talking circuit. I provide an ordinary telephone receiver 5" in series with the secondary of the induction coil 1, and l inter-pose a pair of condensers 9 between the secondary oi the induction coil I and the receiver t on the one hand, and the terminals of relay L on the other, so that while the subscriber by means of switch it can connect his phone Tt for receiving calls over the telephone line, he cannot originate calls thereovcr from the radio telephone extension.

Returning now to the central station, and particularly to the radio department thereof shown in Fig. 3, T represents a broadcasting transmitter, symbolizet in very simple form, but supposed to contain the usual elements of power supply, modulator, oscillator and aerial, with suitable amplification of the audio waves supplied on the input side. The ack d connected to the an'ipliiier t and thence to the transmitter 'l, symbolizes a group oi such jacks or equivalent connecting means such as automatic switches, controlled by dials or keys for connectii any of the wire lines to said radio transmitter. Detailed appliances, both for the switching and for the radio transmission, are well known in the art, and need no specific description in this specification, my present invention having to do particularly with the method of transmitting by wave radiation to the substations, and of bringing in all conversation originating or received at the substation radio telephone over the subscribers wire line. This includes repetition of modulated radio waves received at the radiophone substation and also originating messages gathered up and to be put through the amplifier t on the transmitter T for ln'oadcasting.

.lt may be explained here that the transmitter l for general purposes is assumed to be the standard wave length transmitter for the local exchange area, to which all 01 the substations are tuned and upon which they depend both for original messages and programs and for those received and relayed from a distance. There are special cases, however, in which certain groups of broadcast service subscribers may desire intercon'nnunication among themselves, and I contemplate therefore the installation of duplicates of this transmitter, which may be connected up for such group use. For eX- amplc, chess club desiring to meet, arranges a program, and at the appointed time its members attend at their broadcast receiving sets, all removing their transmitters T from their hooks, while the radio the condensers in its circuit.

operator at the central station plugs up the multiples O'lltll-Glf respective lines through their acks J J, and connects them on to a special broadcasting transmitter of the type T. lChis plugging up may be carried out in any desired manner, there being several ways well known in the art for thus connecting telephone lines together. The radio operator then supervises .the operation, since any one of the connected subscribers may be speaking through the broadcasting transmitter to the others, and it is necessary to prevent interruption. The same might be said of any meeting of a group of people held in this manner, the most valuable feature otf this part of the invention being the absolute control allorded over the transmitted messages. The connection to the broadcasting transmitter is solely within the control oi the radio operator at the jack J or any other suitable form of swi ch, and he has it in his power therefore to cut oil connection at any time.'

The cord circuit between plugs P and P in Fig. 3 is the same as the operators cord circuit in F 2, but the radio operator also has special test cords such as that shown in the upper part 01" the figure connected to plug l. Here the keys KK are of stand ard construction, as in the other cords, and the test contact of the plug P* is connected through suitable resistance to the super-' visory lamp 5 to the radio battery B, means such as the conn'nutator 21 being provided to give special tone test on the test thimbles or the multiple jacks J, [1, J etc. The key K is also provided with suitable contacts, not shown, for applying signal current to the line while holding the relay L energized, the signal ng current being applied in any known or other suitable manner capable of effecting the receiver t or other signaling de vice. For example the ordinary bowler signal current may be applied to the line conductors to operate the receiver 25' through It will be observed that the constant connection Oil the ba;tery wire 24: at the substatiim to the bus wire of the battery 3,, produces charging of that battery by the constant flow oi curent therethrough from the main radio battery B at the central oliice. The amount of energy thus delivered to the battery A, depends upon the size of theJine wires, and the length of time available for such charg ing. As shown, the battery wire 2a is not cut oil except when the cut off relay L" pulls up which is only when the line wire is in use for conversation. With No. 19 line wires, and using only the sleeve wire for conduction, it would be possible to safely transmit from one-halt ampere 'to two or three amperes, according to the line resistance and the voltage of the battery employed. Where this voltage is standard All - "from to ohms, it would be possible to maintain the battery A, continuously charged, provided the time of discharge be not too long extended, and the charging be not interrupted by other contingencies, such as the excessive telephone u.-e of the line. In Fig. l of the drawing I showmeans for charging such a battery over a phantom circuit composed of the two sides of a magneto telephone line. Such a phantom circuit of course possesses still lower resistance than a single wire of the pair and correspondingly augments the amount of eneregy that may be delivered without a pro hibitive loss. I wish to point out in con nection with this, that radio instruments have recently been devised by the commercial radio corporations, and also by the United'States Bureau oi Standards, which employ rectified alternating current for lighting the filaments ot the audion tubes, such currents being stepped down to usual voltage of the filaments from the voltage of house mains or feeder lines. Using such a type of transformerand reotifier circuit, it is within the scope of my invention, to teed the filaments direct, and at the same time charge a floating storage battery A, if desired, by transmitting over my line wire l919-2 la sine wave current at such voltage as will deliver the necessary energy.

Connected to the key; K is a'wire 50 con taining a supplemental key is to connect the voltmeter or other suitable indicating instrument V and ground. to connect the operators listening set, and also to put battery on the tipot' the plug, by which means current'is thrown out on the tip side 18 of the line, then through eX- tcusion 18 and back contact ot relay L, to the winding of relay L and ground. The operation of these-test keys will be obvious from the description. Key It enables the operator to take a reading on the battery A the line resistance being known, and the main batteries B, B being disconnected both at the out oft relays L L tromthe line itself and by theback contacts of key K from the plug P test because the lamp filaments can be observed by the subscriber, and any defect therein reported over the telephone. A companion test however enables the operator to determine whether the broadcast receiving instrument as a whole is functioning properly, assuming the transmitter Tto be hung upon its hook H and as shown to have its mouth piece turned toward the emission orilice or diaphragm of the radio telephone receiver. Connect-ion of battery B to the relay L causes the subscribers telephone set T", l, to be connected to line and so to the The key K serves This is the most important the multiple jack J plug P and the 0perators head phone connected through the listening'key K". It is assumed of course that some form of broadcasting is going on from the transmitter T so that the radio operator not only gets a test on the pertormance oi the individual subscribers 'radiophone, but also gets a test on his own broadcasting transmitter and on the relative t ning of the same with respect to the sub scribers station,

It should be noted that battery 13 in Fig. 3 is connected to the ring wires 17, 19" through the contacts of cut off relays L, L energized in parallel with the line cut oft relays L and L either from the radio board or from the telephone switchboard. This enables the central office under all circumstances to keep a talking line balanced and suppliedwith current only through the connective cord or switch circuit, but as shown in Figs. 5 to 8 inclusive, the conneotions of the radio battery and that of the main battery are such that the balance is normally maintained, and current is supplied in such a way to the ring line that no signaling apparatus on the telephone switchboard is affected thereby.

Fig. 5 shows the condition when a subscriber is talking through the telephone switchboard, the repeating coil I and'the main battery; B being shown as bridged across the line, "and the radio battery B permanently connected through the ring side to the subscribers battery A Battery supply for both the subscribers transmitter and side of the the battery A, would as a matter of tact be drawn in due proportion from each of the centralized batteries B, B, and'the resultant etlect wouldbe to divide the load between the two parallel sources, without changing the normal condition.

Fig. 6 shows the same arrangement when the subscribers telephone station is idle, and the main battery B is bridged across the line wires between the two windings l1 of the subscribers line relay on the telephone switchboard; while the radio battery is connected in parallel to the ring side of the line through low resistance choke "coils ma3" which do not appreciably reduce the potential placed upon the line terminal of which, be-

the winding 1 of the line relay,

ing exposed to balanced potentials, will not be energized unless the subscriber calls.

Figs. 7 and 8 show corresponding conditions wit-h the cut oflf relay L at the subscribers station for detaching the battery A, when the subscriber is talking.

It is not considered necessary to actually adopt a permanent connection ofthe radio battery B because telephone conversations are usually brief and the time of use of the current flow in the sleeve wire would not be thereby greatly curtailed. At the same time I have provided means in the cut oft relays L", L to disconnect the battery B when the lines are plugged up for conversation as at m in Figs. 5 and 7, and when such cut off relays are employed, the choke coils a'-w' may be omitted, so that a practically perfect balance may be had across the terminals of the line relay 1. In other words, by using the cut off relays L, U, of Fig. 3, I am able to dispense with choke coils m-rv and connect the battery or charging genera tor of any type as shown in Fig.

Fig. 9 shows a modified circuit in which the telephone switchboard and radio switchboard are provided with multiple line con nections as before, the radio switchboard having connections to the radio broadcasting transmitter T and the radio operator iaving a full equipment of cords and plugs of known types symbolized at P The substation is provided with a radio detector se and receiver 36, normally connected to the radio detector set through back contacts of the relay L which when energized by means of the operators key 1 0* at the radio board, will disconnect the receiver 36 and connect the radio detector seton its audio side directly to wires and so through the contacts of cut oil relay L to the line wires 1617. As there is no battery shown for the detector set (which is typical only), the radio central battery feed is omitted in this figure, which represents a very simple standardized system in which however the radio operator still has perfect control tor all purposes of the substation broadcast receiver. It should be noted that the continued energization of relay L disables the radio set, and by winding this relay so as to consume little current, this atl'ords. means to discounect the subscribers circuit until an inspector can make his mums and the instruu'ient can be removed.

If it be desired to have no grounds on the radio battery cusses at substations, such as that on the A. battery at station A in ii 1-" 3, the ground wires may be carried thro'. U contacts on switch hook H, opened when the hooks are up. Many other details of operation may be introduced and changes made, without departing from the scope of my invention.

Referring to the modification in which the broadcast isdist-ributed over the wires, indicated in the diagram of 10, it Will be noted that the only portion of the system,

changed is the radio portion, that is the radio operators circuits and the circuits oi the subscribers broadcast receiving station. As the utilization of this wired radio broadcasting system requires no change in the circuits of the land telephone exchange system as previouslydescribed and shown in Figs. 2 and 3, it is only necessary to substitute Fig. 10 for Fig. 3 in disclosing this modification. The conductors 16 17 17, 19 etc. of Fig. 10 tie'on to the conductors similarly designated in Fig. 2. The circuit arrangement of Fig. 10 is substantially the same as Fig. 8 except that instead of the output 01' the radi transn'iitter T being connected to the antenna, it is connected to a wire bus 60 multipled on to the subscribers lines through multiplied pairs 6l6 l, ('32 through suitable switch contacts 63; while at the subscribefls end or the system, the primary side of the coupler circuit 29 is connected directly across the line instead of with a receiving antenna. The ordinary tuning condenser is in series in this connec tion with the line and prevents by-passing of the ordinary telephone currents through the said circuits. To prevent metallic multiple connection between the subscribers lines at the central radio station the line multiples are connected to the radio bus 60 through suitable blocking condensers. At the radio central station are also provided jack connections to the radio bus 60 as represented by the jack J through which the radio relay unit of Fig. 11 may be connected on to the bus.

The operation of this wired radio system is similar in all respects to that of the system previously described and illustrated in the circuit combinations of Figs. 2 and 3 except thatcarrier current broadcast is guided over the subscribers lines from radio transmitter T, and is received at the suhscribefis broadcast receiver from the line wires 19, 18, by way of the bridged circuit 66 connecting with the primary side of the coupler circuit 29. From the coupler connection 25) the detection. amplification, and reception of the signals at the loud speaker 36 are identically the same as that described in connection with 3. The supply circuit for storing the subscribers filament battery A, the radio operators distant control of the subscribers relay If, the radio operators testing and supervisory circuits, and circuit connections of the radio operators multiple jacks J J J for broadcasting intercommunications between the subscribers, are all identically the same as thatdescribed in connection with Fig. 3. In Fig. 10, the telephone transmitter circuit at the subscribers radio substation is the same except that it has been further elaborated over that'of Fig. 3, in that all the necessary contacts to the subscribers talking circuit key it. are shown with their actual connections, to enable the circuits to be readily traced. Fig. 10 also shows a pair of guarding contacts BKBK which may be opened during broadcasting by the subscriber, from his broadcast transmitter T, to give the party at the transmitter T exclusive. use or" the lay, a path line over the land telephone substation and to relieve the line wire 19 of its connection to ground through the battery A. i

It, while broadcasting is being listen in to the audio side of the subscribcrs radio receiver to ascertain the quality of reception, assuming the subscribers transmitter T to be on its switch hook i the radio operator plugs in on the multiple jack J with the testing plug P and depresses his key K which connects the radio central battery B to the tip side of the line and energizes the subscribers cut-on relay L This puts the subscribers broadcast receiver into operation, connects the telephone circuit T H for receiving the audio signals from the loud speaker 36 and connects the circuit from the transmitter t on to the line and there over to the radio operators circuit, all in a manner as previously described in connection with Fig. 3. For the purpose of preventing operation of the cut-oil relay L at central station, during the maintenance of the circuit connections just described, the radio operators test circuitis provided with means for opening the test circuit through which relay L would ordinarily be energized. This means consists of a key having its contact connected in series in the test circuit and bridged by a condenser c to permit passage of the tone test current when the key contacts are opened. Thus, with the contacts of key 70 open, the relay L remaius deenergized preserving the connection of the central station battery with the subscribers broadcast receiver station battery A, while subscribers relay L is held energized over the distant control circuit which is the same as that described in connection with Fig. 3, and which may be traced from radio central battery B, through operators listening key is" tip contacts of plug P and jack J line multiple 18 line wire 18 to subscribers substation A, then by way of branch wire 18, contact of relay L conductor 26, through winding of relay L and ground back to the central station radio battery B. Thus over the line wires there is maintained a path for the operators distant control of the subscribers cut-on' refor power or battery supply from the central station, a pat-h for the super audio broadcastin and a path for audio currents from the substation to the central station for supervision of reception at the substation. The circuit connections which obtain for this condition of service are shown in the simplified or schematic diagram Fig. 12. From inspection of this diagram it will be seen thatbattery is supplied from the central station battery 13 to the subscribers battery A by way of conductors 19 19, contact 27 m subscribers sent out -over the lines, the radio operator desires to the radioway of ground. The relay L is controlled from the radio central station by the connection from battery B through operators listening key 5, line wire 18, relay L back to central station battery by way of ground. Connection for radio transmission from the transmitter T to subscribers broadcast receiver is maintained by way of the radio bus 60, line multiples 62, line wires 18-19 to the primary side of the subscribers coupler circuit 29. Connection for transmission of audio signals from the telephone transmitting circuit at the subscribers radio receiver is maintained by way of contacts of relay L branch wires 2667, line wires 1819, line multiple 1819, and contacts of listening key 70 to the operators listen ing set L When itis desired to have the subscriber A broadcast from the telephone transmitter T at his radio receiving station, the radio operator plugs in on the jack Jtwith his answering plug P and plugs in on the trans mitter input jack J with his calling plug P while the subscriber at substation A actuates the key it which closes the battery supply circuit of his transmitter T and connects the secondary circuit 1 to his line. The subscribefis transmitter or primary circuit may be traced from his local battery A by way of conductor :25, conductor 12, contact of key 72., transmitter T, induction coil primary winding 1, and by way of ground backto the local battery A. The circuit of the secondary winding 1 of the induction coil may be traced across the line wires 18- 19, from wire 18, over branch wire 18, contact of relay L", wire 26, contact of relay L, wire 39, secondary winding 1 conductor 40, contact 27, conductor 67, contact of relay L through branch conductor 19 to. line conductor 19. The subscribers talking circuit being thus connected in bridge of the line is connected on through to the input side of the central ofiice broadcast transmitter by way of the line 1819 multiples 18-19, jack and plug connection (l -P through the cord circuit and plug and ack connection P*J*, and through amplifier t to the input side of the transmitter T- Thetransmitter T, having its output operatively connected with the line wires 1819, as well as other lines of the exchange, the broadcasting subscriber at station A will receive his own broadcast through his broadcast receiving apparatus.

The circuit connections existing during this condition of service are indicated in simplified form in the schematic circuit diagram of Fig. 13. From inspection of Fig. 13, it will be seen that audio currents originating at T will be transmitted over the line to the central station by of conductors 39-40, contacts 27 -27 conductors 26-67,

battery A, and back-to central station by line wires 18-19, radio op'er-ators cor-d cirlib) cult and plug connection JP, amplifier t to transmitter T. The output side of the transmitter T is connected to the line wires l819 through line multiples 62, while the input side or coupler 29 of the subscribers broadcast receiver is connected across the line 18-l9 through the pair of conductors 66, The broadcast transn'iitter T is, of course, multipled to other lines not shown. Thus with the cir nit arrangement of Fig. 13, he subscriber may transmit broadcast matter at audio frequency over the line to the central station and receive at super audio frequency over the same line.

Should it be desired to have a subscriber broadcast from his ordinary land phone substation, the radio operator connects the subscribers line with the input sine oi the broadcast transmitter T through jack J, plug P P J input amplifier t to radio transmitter T. The subscriber is now supplied with telephone transmitter current and has telephonic connections over the line as in the usual land phone system except that his ba tery supply line supervision and other connections are maintained through the radio operators cord circuit instead of through the telephone exchange switch boards. The output side of the transmitter T is connected to the various line wires as before described so that intelligence sent out by this subscribei"s station is sent back over his own line. and other lines in the form of wire guided radio, which may be picked up by the different subscribers broadcast re eeivers through their coupler connections 29 and multiple pairs 66 tapped to their respective line wires.

ne connections maintained during this ionditiim oi service are shown in the simpli lied or schematic diagram of 14., where it will be seen. that the broadcasting subscriber at station A is supplied with transmitter current from the central. ofiice battery over the line wires 18-19, and that the receiver or outgoing telephone circuit is connected across the line, all in the usual and well known manner of land phone practice. The exception is that the subscribers line 18 19 is connected through the raoio operators plug and acl; connection PJ, and the input amplifier z? to the input side of the radio or broadcast transmitter which has its output end connected to the lines for wire guided broadcasting. This broadcast may be taken off the line wircs18-19 at the broadcast receiver station-of the broadcasting subscriber, as well as the broadcast receiving stationot other subscribers, through the coupler connect-ion 29 and multiple pair 66 con nected across the line wires. It will be noted that during this connection the subscribers broadcast cut-oil re If is cner gized, maintaining its contacts open and thereby relieving the line 01' all straight from the central station to the substation.

In the simplified diagram, Fig. 15, I have shown a form of the invention in which the means for enabling the radio operator to listen in on the audio reception at the subscribers broadcast station, is simplified. This consists in providing means for elec trically connecting the audio output circuit of the subscribers broadcast receiver across the line wires 1819, through suitable switching and coupling means. This connection is established by closure of the switch contacts 73, and 70 which connects the audio circuit of the broadcast, receiver across the line wires byway of primary winding 69 of the repeat coil RC, secondary winding 68, contacts 70, branch wire pair 71 to line wires 18-19.

In the operation of this circuit arrangement the radio operator communicates with the subscriber either over the land phone or by vway of the broadcast system and instructs him to establish the test circuit cone nections by closing the contacts 73 and 70, whereby the radio broadcasting sent out from transmitter '1 over the multiple conductor 65 and line 18-19, is received at the subscribers broadcast receiver through the coupler connection 29, transformed into currents of audio trequency and sent back by way of contacts 73, repeat coil BC, branch wires 71, line 1819, to the radio central station and thence through contacts of the radio operators listening key is to thelistening set L. At the same time, battery charging current is transmitted from the central ollice battery B over line wire 19 and contacts 741 to the subscribers filament battery A. It will be seen that with this arrangement of circuitconnections the line wires 1819, as in the arrangement of Fig. 14, serve to simultaneously transmit poweror battery supply from the central station to the substation, to transmit radio frequency currents from the central'station to the substation and to transmit audio frequency currents from the sub tation to the radio station. 7 l

I claim:

1. The combination of a plurality of telephone substations, a central station, a line radio broadcasting transmitter at said central station, a receiver therefor at each substation, a wire line connecting each substation with the central station and a telephone on each line at each substation, with means at the central station to direct modulated waves from W said broadcasting transmitter over said wire lines, to said receivers, other means to interconnect the substatlons for "conversation through said wire lines, and

means "also at said central station supplying operating energy to the receivers-at the substations each over its individualwire line.

2. A combinedtelephone and line radio broadcasting system, connjrising a plurality of telephone substations, a telephone and a high frequency receiver at each substation, a. centralistation common to said substations, individual vline wires v interco'nnecting, the centralstation and the substations, mea'nsto direct high frequency modulated waves over said linewires to the substation high frequency receivers, and common means at the central station supplying woperatingjcurrent to both telephones and high frequency receivers over their respective individual line wires, differentiate between the high frequency waves, operating current and the telephone currents, and to prevent interference, 7

3..'In a broadcasting systenn a mainstation,,.ja plurality of substations, jand, individual wire circuitsfromthemain stationtQthesubstations, means at sa d main station for generating and transmitting over said wire circuits to the ubsta ions high frequency mo'dulated ,waves, ,meansat the substations for. receivingsaid waves, with means at. the main station controlling the wave receiving means at the substations over said wire circuits A In abrQ d stmgis m, m ns tion', a plurality of .substations,- and individualwire circuits from the main stat on to the substations, meansat s aid main station for generati ng and transmitting over said wire circuitsdo the substations high frequency modulated waves, means at the subete f r, rew r g aid; Wav w t a centrali e sources? urren u ly, f t Su atio ar e vi g. ,meen -te n t sail wire, ,circuits and distributed thereby ii li ilil.

substations.

I, broadcasting q a primary station, a secondary distributing station, and a plurality of lo cal, ,recei ving stat ons connected through wire lines .to the senders .:r i 2i v a all pe man t, tun th ewit em e Q said e ndary a i to e' e re b castw te from Pri ar il t oe Mite wa el gt an t0 (rel y, and redistribute the same over saiu wim lines in its own I W i i V g' tati ea e li lnfi i an e n l o S i ee tlaryt i e d termine over said wire'line's its transmitter isactually tuned to the fiired wave length of its receiving stations.

tut 'li' 'ne system; a transmit- '6.Inarad H receiving station, a line radio ting station,

with means at' each substation ,to'

ally and directly to the severab l'iigh frequency r area. at .the standard wavelength to 1 cation comprising; central station, rali'ty'of' substations related thereto, and ntransmitter at the transmitting "station, for

transmitting: high frequency .niodu'lated waves, a :receivin-gset at the receiving station-tuned to Ii 9: said waves, and a-wi-re circuit connecting the two stations with means to connect-it from saidlinemadio transmitter through-[local wave receiving connections to the receiving set at the receiving station, and means at 1 the transmitting stat-ion; to control said connecting means,

- operable through said wire "circuit to maintain said secondary station :transmitting means in constant tune with said local station receivingsets'.

vg8." The combination 'ofa 1urality of sub stations, a central station, 21' inc radio broadcasting transmitter at 7 said: central station, a high frequency receiver at 'e'acl'i substation, a wire line connecting each substati'on with the central station and a telephone on each line-at each substation, with means at the central station to interconnect the substations for conversation through-said, wire lines', means also at said central station controlling the 'o-p'erationof-the high freqiiency receivers at said substations over said: wire lines, and other means to connectsaid line wire's individu'ally to said line fradibxbroadfcas'tin'g transmitter, so-"as: to transmit high frequency modulated waves thereover to the subscribers receivers. .1 v

, 9;The c'ombination of aplur'al-ity ofsubstations, a centralstation, a line radio b'roadcasting transmitter at said central station,- a

a wire line connectinggeach substation with the central station and a telephonefon each line at each substation, with means at the central station to interconnect: the substations for conversation through said wire' lines; means at said-central station to connect end use radio bruad'casting transmitter with said w1re- ,l1nes, and means also at said central station for connecting and 11180011- 'n'ectin'g thehrgh frequency receiving appaeceiv'e'r 1 at each substation,

ratus at said "substations from said wire i lines.

10', A line'radi'o system of iiitercomrhiiniupl dividual circuits interconnecting the same,

' be returned over the wire circuit in the other direction, with means at the central station to control the transmitting means at each substation over thesame wire line.

frequency waves and the wire currents on said wire line so that modulated high frequency waves may be transmitted in one direction, and corresponding demodulated low frequency waves may be returned over the wire circuit in the other direction, with means at the central station to control the receiving means at each substation over the same wire line. 7

12. A line radio system of intercommunication comprising a central station, a plurality of substations related thereto, and individual circuits interconnecting the same, each circuit composed of a high frequency link and a low frequency return, both related to and guided over the same wire line, and transmitting and receiving means located at the central station and at the substations, adapted to inter-relate the high frequencywaves and the wire currents on said wire line so that modulated high frequency waves may be transmitted in one direction, and corresponding demodulated low, frequency waves may be returned over the wire circuit in the other direction, with means at the central station to control the-transmitting and receiving means at each sub station over the, same wire line. Y

13. A line radio system of intercommunication comprising a central station, a plurality of substations related thereto, and in- 'dividual circuits interconnecting the same,

each circuit composed of a high frequency link and a low frequency return, both related to and guided over the same wire line, and transmittmg and receivlng means l cated at the central station and at the substations, adapted to inter-relate the high frequency and the wire currents on said wire line so that modulated high frequency waves central station to control the substation operation over the same wire line.

14. A line radio system of intercommuni cation comprising a central station, a plurality of substations related thereto, and individual circuits interconnecting the same, each circuit composed of a high frequency link and a low frequency return, both related to and guided over the same wire line, and transmitting and receiving meanslocated at the central station and at the substations, adapted to interrelate the high fre quency waves and the wire currents on said wire line so that modulated high frequency wavesmay be transmitted in one direction, and corresponding demodulated low frequency waves may be returned over the wire circuit in the other direction, with switches at the substations controlling the relation of received and transmitted waves, and means at the central station for controlling said switches over the same wireline.

15. A combined telephone and line radio broadcasting system comprising a plurality of telephone substations, a telephone central station, line wires'interconnecting them, a plurality of line radio substations, a line radio central station, means to transmit messages from said line radio central station over said line wires to its substations by modulated high frequency waves, means at the line radio substations to transmit messagesover same line wires t'elephonically, wire connections between the line radio substations and the telephone substations, and wire connections between the'line radio central station'and the telephone central station.

16. A combined telephone and line radio broadcasting system comprising a plurality of telephone substations, a telephone central station, line wires interconnecting them, a plurality of line radio substations, a .line radiocentral station, means to transmitmessages from said line radio central station over said linewires to its'substations by modulated high'frequen'cy waves, means at the line radio substations to transmit messages over same line wires telephonically, wire connections between the line radio substations and the telephone substations, and wire connections between the line radio central station and the telephone central station, together with means controlled a telephone subscriber in calling to disconnect the wire connections between histelephone and the corresponding line radio re ceiver.

17. A combined telephone-andline radio broadcasting system comprisingv a plurality of telephone substations, a telephone central station, line wires interconnecting them, a plurality of line radio substations, a line radio central station, means to transmit messages from said line radio central station.

over said line wires to its substations by modulated high frequency waves, means .at'

the line radio substations to transmit messages over same line wires telephonically,

'ofthe line radio and means also at said line radio substations'for effecting telephone connection with the corresponding line circuit.

18. A combined telephone and line radio broadcasting system comprising a plurality of telephone substations, a telephone central station, line wires interconnecting them, a plurality of line radio substations, a line radio central station, ineans to transmit niessages from said line radio central, station over said line wires to its substations by modulated high frequency wav s, means at the l'ine 'radiosubsta'ti'ons to transmitmessages over same line wires telep'lionically,

wire connections betweenthe line radio substations and the telephone substations, and wire connections between the line radio central station and the telephone central station, and means controlled by anoperator at the line radio central station to connect and disconnect the wi'r'e circuits for telephonic communication between each line radio substation and the corresponding telephone substation.

19. A combined telephone and line radio broadcasting system comprising a plurality of telephone substations, a telephone central station, line wires interconnecting them, a plurality of line radio substations, a line radio central station, means to transmit messages from said line radio central station over said line wires to its substations by modulated high frequency Waves, means at the line radio substations to transmit messages over same line wires telephonically, wire connections between the line radio substations and the telephone substations, and wire connections between the line radio central station and the telephone central station, together with a centralized source of current supply ateach of the central stations, both said sources feeding independently through the line wires to the telephone substations and to the line radio substations respectively.

20. A combined telephone and line radio broadcasting system comprising a plurality of telephone substations, a' telephone cen central tral station, line wiresint'erconnecting them,

substations and to the line radio substations respectively, and means cont-rolled an operator at the ,telephone central station to disconnect the line radio central battery from a line when in use for telephonic conversation.

g 21. A combined telephone and line radio system ofintercomniunication comprising a station, subscribers substations, means for interconnecting said subscribers substations through thecentral station for conversation, line radio means for broadcasting said interco nmunicating conversation,

line radio receiving means atthe substations, and means at the central oflice for supervising thereception at saidsubstations.

.22. In a broadcasting system, a central station, a plurality of substations, means at said central stationfor generating and transnitting to the substation modulated high frequency waves, means at the substations for receiving said waves, individualwire circuits from the main station to the substations, with means at the main station controlling the wave receiving means at the substations over said wire circuits, and means for putting a characteristic busy test signal on an individual wire circuit during the control of the wave receiving means associated with the said individual wirecircuit. I

23. A combination telephone and line radio broadcasting system comprising a plurality of telephone substations, a telephone central station, line wires interconnecting them, a plurality of line radio substations, a line radio central statioin means to transmit messages from said line radio central station to its substations by modulated high frequency waves, means at the line radio substations to transmit messages telephonically, wire connections between the line radio substations and the telephone substations, wire connections between the line radio central station and the telephone central station, a source of direct current supply at the telephone central station feeding through the line Wires to the respectivetelephone substations, storage batteries at the line radio substations 

